Conventionally, a liquid crystal display device has been widely used as a display device. In particular, an active matrix liquid crystal display device has been widely used as a display device.
The active matrix liquid crystal display device includes switching elements in its respective picture elements. The active matrix liquid crystal display device further includes a plurality of scanning signal lines and a plurality of image signal lines, which are provided so as to intersect each other to control the switching elements. The switching elements are provided at respective intersections of the plurality of scanning signal lines and the plurality of image signal lines. Further, there are provided picture element electrodes, which are connected with the respective switching elements, so as to correspond to the respective picture elements.
(Alignment Modes)
For such a liquid crystal display device, a variety of alignment modes of liquid crystal molecules have been proposed. The following description discusses the alignment modes of liquid crystal molecules.
For example, there have been proposed, as the alignment modes of liquid crystal molecules, (i) a TN (Twisted Nematic) mode in which an alignment direction of liquid crystal molecules near one of substrates is at an angle of approximately 90 degrees with an alignment direction of liquid crystal molecules near the other one of the substrates, (ii) a VA (Vertical Alignment) mode in which an alignment direction of liquid crystal molecules is almost perpendicular to the substrates, and (iii) the like.
Particularly in a case of the VA mode or the like, a plurality of alignment regions, i.e., multiple domains, can be made in each of picture elements so as to improve viewing angle dependence. In order to achieve the multiple domains, there have been proposed (i) a configuration in which each of picture element electrodes has slits that extend in a direction that is different from domain to domain and (ii) the like configuration.
For example, Patent Literature 1 describes a configuration in which each of subpixel electrodes (the picture element electrodes) has slits that extend in a plurality of different directions, thereby achieving a plurality of alignment regions.
(Vertically Long Picture Element Electrode)
The following description discusses a shape of each of the picture elements in the liquid crystal display device.
Generally, each of the picture elements has a vertically long shape. Accordingly, the picture element electrodes that correspond to the respective picture elements each have the vertically long shape. This will be described with reference to (a) of FIG. 8. (a) of FIG. 8 illustrates how picture elements 14 are arranged in a liquid crystal display device 10 that is capable of color display.
As illustrated in (a) of FIG. 8, in a case of color display, there are provided three types of picture elements 14: picture elements 14 that display R (red), picture elements 14 that display green (G), and picture elements 14 that display blue (B).
Each of the picture elements 14 that display R, each of the picture elements 14 that display G, and each of the picture elements that display B constitute a group. This group serves as a pixel 16.
In view of for example necessity of displaying a more natural image with respect to a viewer of the liquid crystal display device 10, the pixel 16 generally has a substantially square shape. On the other hand, in many cases, the liquid crystal display device 10 has a shape of horizontally long rectangle, therefore, each of the picture elements 14 has the vertically long shape so that a larger number of signal lines can be drawn toward a longer side of the rectangle.
Specifically, the pixel 16 is divided into three parts that are adjacent to one another in a horizontal direction, which three parts consist of a picture element 14 that displays R, a picture element 14 that displays G, and a picture element 14 that displays B, in such a manner that each of these picture elements 14 has the vertically long shape. This makes the pixel 16 correspond to (i) three of signal lines that extend in a vertical direction (i.e., a plurality of image signal lines 34) and (ii) one of signal lines that extend in a horizontal direction (i.e., a plurality of scanning signal lines 32). Accordingly, the number of signal lines that are drawn toward the longer side of the horizontally long rectangle is greater than the number of signal lines that are drawn toward a shorter side of the horizontally long rectangle.
Further, each of picture element electrodes 60 is provided over a substantially entire area of a corresponding one of the picture elements 14. Therefore, each of the picture element electrodes 60 also has the vertically long shape, which corresponds to the vertically long shape of the corresponding one of the picture elements 14.
(Horizontally Long Picture Element Electrode)
Besides the configuration in which the vertically long picture element electrodes 60 are provided, there has also been proposed a configuration in which horizontally long picture element electrodes 60 are provided. This configuration has been proposed for example to reduce power consumption by reducing the number of the plurality of image signal lines 34. This will be described below with reference to (b) of FIG. 8. (b) of FIG. 8 illustrates, as is the case with (a) of FIG. 8, how picture elements 14 are arranged in a liquid crystal display device 10 that is capable of color display.
As illustrated in (b) of FIG. 8, according to the liquid crystal display device 10 that includes the horizontally long picture element electrodes 60, a pixel 16 is divided into three parts that are adjacent to one another not in the horizontal direction but in a vertical direction. This makes the pixel 16 include three horizontally long picture elements 14, which consist of the picture element 14 that displays R, the picture element 14 that displays G, and the picture element 14 that displays B.
Since each of the picture elements 14 has the horizontally long shape, each of the picture element electrodes 60 also has the horizontally long shape, which corresponds to the horizontally long shape of each of the picture elements 14.
According to this configuration, although the number of horizontally-extended signal lines (i.e., a plurality of scanning signal lines 32) that correspond to the pixel 16 increases to three, the number of vertically-extended signal lines (i.e., a plurality of image signal lines 34) that correspond to the pixel 16 can be reduced to one. This makes it possible to reduce the number of drivers for the plurality of image signal lines 34, which drivers generally are more expensive to manufacture and consume more power than drivers for the plurality of scanning signal lines 32. As a result, it is possible to reduce power consumption and production costs.
In addition, the drivers for the plurality of scanning signal lines 32 each have a circuit configuration less complicated than that of the drivers for the plurality of image signal lines 34. Therefore, the circuit of each of the drivers for the plurality of scanning signal lines 32 can be provided, when the plurality of scanning signal lines 32 and the plurality of image signal lines 34 are formed, on a substrate on which the plurality of scanning signal lines 32 and the plurality of image signal lines 34 are provided, thereby further reducing the production costs. Further, since the drivers for the plurality of scanning signal lines 32 each have the circuit configuration less complicated than that of the drivers for the plurality of image signal lines 34, a driver mounting area can be reduced in its area size. This contributes to downsizing of the liquid crystal display device 10.
(Patent Literature 2)
The liquid crystal display device that includes the horizontally long picture element electrodes is described in for example Patent Literature 2. That is, Patent Literature 2 describes a liquid crystal display device that includes, for the purpose of reducing production costs and power consumption, picture element electrodes each of which is long in a direction in which scanning signal lines extend.
Citation List
Patent Literature 1
Japanese Patent Application Publication, Tokukai, No. 2006-189610 A (Publication Date: Jul. 20, 2006)
Patent Literature 2
Japanese Patent Application Publication, Tokukaihei, No. 11-167127 A (Publication Date: Jun. 22, 1999)